1. Field of the Invention
The invention relates to an elongated cylindrical member, such as an axle, bolt, or the like, having means for the in situ detection and indication of cracks therein.
2. Description of Prior Art
Cracks in axles and bolts have contributed to severe accidents in railway cars, airplanes, and other moving vehicles. These cracks are often hairline cracks which cannot be easily visually detected. Yet quite often, the bolts and axles are only visually inspected. Of course, means do exist for the mechanical and/or electronic inspection of axles and bolts and the like, but they are relatively cumbersome and can be used under only special conditions. Thus, such mechanisms cannot be used when the vehicles are in motion.
The prior art also teaches various strain indicators for bolts as exemplified in U.S. Pat. No. 2,562,831, issued July 31, 1951 to A. R. Stone; U.S. Pat. No. 3,772,759, issued Nov. 20, 1973 to T. W. Bunyan; U.S. Pat. No. 3,799,108, issued Mar. 26, 1974 to J. E. Mosow; U.S. Pat. No. 3,841,193, issued Oct. 15, 1974 to A. Ito; U.S. Pat. No. 4,002,139, issued Jan. 11, 1977 to W. J. Payne; and U.S. Pat. No. 4,041,776, issued Aug. 16, 1977 to W. J. Payne. However, such strain indicators detect only the tightening strain applied to the bolts; they do not detect the presence or absence of cracks in the bolts. In addition, these machines can be used only under static conditions.
All of the above-mentioned mechanisms are further characterised by the fact that they exist separately of the bolts, axles, etc., and do not constitute a part of the bolts, axles, etc., themselves.